Field of the Invention
The invention relates to the use of N-(1,3,4-Oxadiazol-2-yl)arylcarboxamides or their salts for controlling unwanted plants in areas of transgenic crop plants being tolerant to HPPD inhibitor herbicides.
Description of Related Art
WO2012/126932 discloses several new N-(1,3,4-Oxadiazol-2-yl)arylcarboxamides and their use as HPPD inhibitor herbicides for weed control.
However, the herbicidal activity of N-(1,3,4-Oxadiazol-2-yl)arylcarboxamides might cause damages on several crop plants which limit their use in such crop growing areas as herbicides for weed control.
HPPD inhibitor herbicides can be used against grass and/or broad leaf weeds in crop plants that display metabolic tolerance, such as maize (Zea mays) in which they are rapidly degraded (Schulz et al., (1993). FEBS letters, 318, 162-166; Mitchell et al., (2001) Pest Management Science, Vol 57, 120-128; Garcia et al., (2000) Biochem., 39, 7501-7507; Pallett et al., (2001) Pest Management Science, Vol 57, 133-142). In order to extend the scope of these HPPD inhibitor herbicides, several efforts have been developed in order to confer to plants, particularly plants without or with an underperforming metabolic tolerance, a tolerance level acceptable under agronomic field conditions.
Meanwhile transgenic plants have been engineered by by-passing HPPD-mediated production of homogentisate (U.S. Pat. No. 6,812,010), overexpressing the sensitive enzyme so as to produce quantities of the target enzyme in the plant which are sufficient in relation to the herbicide has been performed (WO96/38567).
Alternatively, transgenic plants have been generated expressing HPPD proteins that have been mutated at various positions in order to obtain a target enzyme which, while retaining its properties of catalysing the transformation of HPP into homogentisate, is less sensitive to HPPD inhibitor herbicides than is the native HPPD before mutation (for example see at EP496630, WO 99/24585).
More recently, the introduction of a Pseudomonas HPPD gene into the plastid genome of tobacco and soybean has shown to be more effective than nuclear transformation, conferring even tolerance to post-emergence application of at least one HPPD inhibitor (Dufourmantel et al., 2007, Plant Biotechnol J. 5(1):118-33).
In WO 2009/144079, a nucleic acid sequence encoding a mutated hydroxyphenylpyruvate dioxygenase (HPPD) at position 336 of the Pseudomonas fluorescens HPPD protein and its use for obtaining plants which are tolerant to HPPD inhibitor herbicides is disclosed. Further mutants of the Pseudomonas fluorescens HPPD protein comprising mutations at various sites and their ability to confer resistance to certain HPPD inhibitor herbicides are described in the PCT application filed (on Sep. 13, 2013) under the PCT application number PCT/US2013/59598 and claiming priorities of U.S. 61/701,037 (filed on Sep. 14, 2012), U.S. 61/766,057 (filed on Feb. 18, 2013), and U.S. 61/790,404 (filed in Mar. 15, 2013).
Some of these mutants, i.e. mutants of the Pseudomonas fluorescens HPPD protein (i) comprising an E (Glu)->P (Pro) replacement at position 335 and a G (Gly)->W (Trp) replacement at position 336 (named PfHPPDEvo33 and being disclosed herein under SEQ ID No:6 in PCT/US2013/59598), (ii) comprising an E (Glu)->P (Pro) replacement at position 335, a G (Gly)->S (Ser) replacement at position 336, and an A (Ala)->E (Glu) replacement at position 340 (named PfHPPDEvo40 and being disclosed under SEQ ID No:8 in PCT/US2013/59598), or (iii) comprising an E (Glu)->P (Pro) replacement at position 335, a G (Gly)->W (Trp) replacement at position 336, a K (Lys)->A (Ala) replacement at position 339 and an A (Ala)->Q (Gln) replacement at position 340 (named PfHPPDEvo41 and being disclosed under SEQ ID No:16 in PCT/US2013/59598) are hereby incorporated by reference concerning the production of the respective transgenic plants conferring tolerance to HPPD inhibitor herbicides under its abbreviations PfHPPDEvo33, PfHPPDEvo40, and PfHPPDEvo41, respectively.
In the before, the amino acid named first characterizes the amino acid being present in the wild-type Pseudomonas fluorescens HPPD protein and the character given in the brackets identifies the respective amino acid in the 3 letter code, whereas the character given in front of the brackets identifies the respective amino acid in the 1 letter code.
In WO 04/024928, the inventors have sought to increase the prenylquinone biosynthesis (e.g., synthesis of plastoquinones, tocopherols) in the cells of plants by increasing the flux of the HPP precursor into the cells of these plants. This has been done by connecting the synthesis of said precursor to the “shikimate” pathway by overexpression of the prephenate-dehydrogenase (PDH). They have also noted that the transformation of plants with a gene encoding a PDH enzyme makes it possible to increase the tolerance of said plants to HPPD inhibitors.
In WO 2002/046387, a gene obtained from Avena sativa encoding an HPPD was described to generate plants overexpressing such gene and thereby causing tolerance to various HPPD-inhibitor herbicides.
In WO 2008/150473, the combination of two distinct tolerance mechanisms—a modified Avena sativa gene coding for a mutant HPPD enzyme and a CYP450 Maize monooxygenase (nsf1 gene)—was exemplified in order to obtain an improved tolerance to HPPD inhibitor herbicides, but no data have been disclosed demonstrating the synergistic effects based on the combination of both proteins.
In WO 2010/085705, several mutants of the Avena sativa HPPD were described as well as plants comprising genes encoding such mutated HPPD and thereby causing an increased tolerance to various HPPD-inhibitor herbicides compared to non-mutated HPPD.
In WO 2012/021785, several mutants along HPPD proteins of various organisms, preferably HPPD obtained from maize were described. Data were obtained from such mutated HPPD enzymes in vitro as well as from plants comprising genes encoding such mutated HPPD and thereby causing an increased tolerance to various HPPD-inhibitor herbicides compared to non-mutated HPPD.
Recently, several new genes encoding HPPD enzymes from various organisms have been identified and employed for obtaining crop plants that show an agronomically useful level of tolerance concerning the application of various HPPD inhibitor herbicides, like such (i) obtained from bacteria belonging to the subfamily Synechococcoideae and certain mutants thereof as disclosed in WO2011/076877(PCT/EP2010/070561), (ii) obtained from protists belonging to the family Blepharismidae as disclosed in WO2011/076882 (PCT/EP2010/070567); (iii) obtained from bacteria belonging to the genus Rhodococcus and certain mutants thereof as disclosed in WO2011/076892 (PCT/EP2010/070578); (iv) obtained from Euryarchaeota belonging to the family Picrophilaceae and certain mutants thereof as disclosed in WO2011/076885 (PCT/EP2010/070570); or (v) obtained from bacteria belonging to the genus Kordia and certain mutants thereof disclosed as in WO2011/076889 (PCT/EP2010/070575) and which are hereby incorporated by reference concerning the production of the respective transgenic plants conferring tolerance to HPPD inhibitor herbicides.